US2920654A - Hydraulic weighing scale - Google Patents

Description

Jan. l2, 1960 w. M. wlsE 2,920,654

HYDRAULIC WEIGHING SCALE Filed April 13, 1956 r/v//f EN. /mw A i /05 464;(525' 4. 25 go Il I I P 53" 2@ j? 54 25 .En BY Ulllited Seres, llaffnf 2,920,654 HYDRAULIC WEIGHnvG SCALEV WilliamM. Wise, Royal Oak, Mich. Application April 13, 1956, serial No. 578,069

' p 1 4 claims. (ci. y137-778) This invention Arelates to hydraulic weighing scales, and particularly to improvements in the construction of weighing scales of the general classdisclosed in my Patent No. 2,643,873, issued June 30, 1953.

Y An important Vobject of the present invention is to provide an improved scale of the indicated variety, utilizing load sensing means comprising a' cylinder, a piston, and an interposed liquid adapted to be pressurized by the load, the `scale being so designed and constructed that frictionV within theload sensing means. is reduced to an absolute minimum.

11A further object is to provide such a scale which is highly resistant to variation of its characteristics due to. wear of parts, and the accuracy of which is not disturbed by the imposition of lateral forces.

A further object'is to provide such a scale which is relatively simple and. inexpensive to construct and to assemble, `as well as to charge and adjust.

Another object is to provide such a weighing `scale which is capable of handling very heavy loads `and which is itself of minimum weight.

Other objects and'advantages of the invention will become apparent-upon yconsideration of the present disclosure in its entirety. 'i v In the drawing: Y Figure 1 is a side elevational view of a weighing scale incorporating thepresent invention; and

' Figure 2 is a view on a larger scale, principally in longitudinal diametriccross section, but partly in elevation, of the load sensing portionsy of thescale.

Referring now to the drawing, Ywherein my invention is illustrated in a crane scale mechanism, referencecharacter designates generally a steel cylinder within which a piston assembly generally designated 12 is movably mounted, in such manner as to pressurize, in proportion to the load of the scale, a 4quantitytof a suitable liquid such as oil- (not shown) which fills the cylinder space 14 and which also fills communicating passages which are not fully shown but which include the connecting tube 18, and a pressure responsive portion which will be referred to hereinafter.

The piston assembly 12 is rigidly connected to a suspension eye generally designated 15 which is adapted to be suspended from a crane hook or other suitable support, and thel cylinder is rigidly held against axial movement with respect to a hook assembly generally designated 16, from which a load to be weighed is adapted-to be suspended. 'The suspensionv eye 15 and hook 16 may of 18 to suitableloadrindicating means (not shown) which may comprisea Bourdontube-type or other appropriate pressure' gaugehousedwithin acasing portion 20 rigidly attached .as by ange ands'crew portions 22, 24 to the side ofr the .vcylinden 10,v the ,casing 20 in turn supporting -a housing. portion -25 fora dial andpointer, byY which y 2 an indication of weight may be given. Such features are shown in my patent above referred to and are known inthe art. n

As itsupper endthe cylinder is partially closed by a head ring 26 having a concentric cylindrical internal wall 281 lThe cylinder is provided at its upper extremity with an inwardly projecting concentric flange portion 30 which is of lesser axial length than and overhangs a part of the head ring 26. The lower portion of the head ring has -a lflange portion 32 which projects outwardly to underliezthe inwardly directed cylinder flange 30. The head ringt'26 isv inserted from the lower end of the cylinder yand is locked against upward displacement by the graduated diameters of such overengaging flange portions -30, 32.. The head ring is alsofsecured in place by -radial'lock screws as 33. A perfect sealy between the cylinder andhead lring is insured by an O-ring 34 fitted in a suitableperiph'eral groove in the head ring and compressed between the head ring and cylinder wall.

The piston 12 has a reduced upper extremity or neck 35 which has an easy sliding fit in the bore 28 in the heardV ringl 26 and which is provided .with a peripheral 4groove 36 in which an O-type sealing ring 38 is fitted,

which maintainssealing engagement with the surface 28 of 'the' head ring. At its upper extremity the reduced piston portion 35 is provided with a peripheral rabbet 40 havinga lat bottom surface 42 and in which a herdenedI steelwear ring 44 is tted and held fast with respect to `the piston. .fThe ring 44 is provided with a smaller peripherahrabbet 45. at its lower end which coacts withathe flat surface42 to deline a peripheral groove within which aplurality of bearing balls 46 are accommodated. ,The ring 44 and the inner surface of head ring 46 are hardened, so that they will not be worn substantially by the hardened steel balls 46, but the main -body portion of the piston 12 need not be hardened.

The central portion 69 of the piston is-y accurately nishedto haveV a very slight clearance with respect to the internal wall 77 of the cylinder and is sealed with respect thereto by an 0-ring 73 carried by the piston.

The `straight cylindrical stem portion 48 of the suspension eye 15 is held against upward displacement with respect to vthe piston by a lock ring assembly 50 formed in two `semi-circular halves and projecting radially inwardly into a peripheral groove 52 in the shank 48 and also projecting radiallyoutwardly from the shank to partially underlie the upper wall 53 of a counterbored portion 54 formed concentrically in the lower extremity of the'y piston 12. The diameter of the downwardly lopeningfcounterbored portion 54 substantially exceeds theoutsidepdiameter of the ring assemly 50, and a filler ring.5 5 is fitted in the counterbore around the ringassemlbly 50 toprevent outward displacement of the two sections `of the latter. The retaining ring 50 is heldin place by an internal snap ring 56` fitted in an internal slot (undesighated) Ain the counterbored portion 54, below the retain- .ing ringv The shank 48 of the suspension eye projects downwardly below the piston and forms a lower bearing-supporting portion, being extended through a cylindrical opening 58 in a bearing wall 60 which extends across the `cylinder spacedly beneath the piston and which is pressed or otherwise rigidly secured in place. The bearing wall 60 mayV also be formed of steel, and its cylindrical internal bearing surface, which is concentric with the cylinder,

is hardened. A bearing ring 62is secured to the lower end ofthe shank in a position opposite the bearing Wall 58, andl is provided with a peripheral groove 64 in which a series of hardened steel bearing balls 65 are tted. The ring 62, or at least the outer face portion having the ball groove therein, is also hardened.

Theskirt of the piston 12 is cut away in an area, des- `acarrear below the piston head portion 70 to the lower end of the piston.. The upper end: of the cutaway portion 68 preferablydefines a truncatedeon'ic' wall 71`which`, at its lower end, joins a vertical-cylindrical `wall 72 spaced outwardly from vand surrounding the counterbored; lpoi",- tion 5.4. The inclination of the wall `71 may besuch as to reinforce'the head 7l) against which the principal pres'- sure resulting from loading of the scale is exerted.

. All ofthe parts except the shank 48 are fitted into the cylindern from thel lower end, the cylinder being counterbored in a plurality of steps of successively graduatedly `load of200,000J lbs. Therpowerr required to distort the rO-rings is accordingly very l`low. In addition, it is unidecreasing diameter upwardly from the lower end. Such f counterborings of the cylinder are performed in such manner 'as to provide a'shoulder 66 to limit upward movemerit of thebear'ing wall 60 and accurately locate the latter.

The lower end of the cylinder is closed by a head gen.- erally/ designated 75 which may, as shown, be providedat its lower end with an externally threaded portion 76 screwed into. a conformably internally threaded portion V77 at the lowerend of the cylinder, and suitably locked in place, as byrlock screw means. 78. The lower head 75 extends upwardly within the' cylinder yand is provided with a relatively deep axial counterbore 80 at its upper end communicating with an .axial bore 82 extending' vdownwardly and completely through the head.

The shank 84v of the hook 16 extends upwardly throng the bore 82 and counterbore 80 and isl provided within the area surrounded by the counterborey with a peripheral groove y85. A lock ring 86 is tted .into and' projects radially outwardly from the groove 85' and may be formed form at each actuation of the scale, and does not introduce static friction. The reduced upper neck 35 and ring 44, fitted within the top head ring 26 are valso freely slidable in the bore 28, and the ring 62 has a free sliding fit in the bearing ring v60. The neck 35 and the downwardly projecting portion 48" of stem 48 are accurately centered by the bearing balls 46j and' 65 respectively, so that these portions, act as pilots for the piston, and it will be appreciated' that friction is held to an absolute minimum by the reduction in diameter of such pilot parts which are mounted in the ball bearings. By reason of the wide vertical spacing of the two' bearings dened by the balls 46-65, any nonaxial loads tending to tilt the piston with respect to the cylinder apply minimum radial loads to the balls and races, so that they cannot be dis- `tortedrenough to introduce appreciable statirc'frictionl AOnly the surfaces. .which are directlyengaged by the balls 'need behard'ened and such'surfaces are carried byy parts travelfis very slight, as indicated above, it is advantageous to minimize any variation of pressure below thepisfion. yinasmuch as scales. of this typel may be left out ondoors in all; kindslfof weather, it is also advantageous to formthe lowerhead 75 as a closure; as shown, even in two semicircular sections, as'in the' case of thelrin'g t 50, andrsimilarly held against escape fromthe groove rby a retaining ring 88 which fills the radial space be.-

tween the ring 86 and the internal-wall of the counterbore 80 and vblocks escape of the sections ofthe ring-86.

Upward escape of the filler ring 88 is prevented by aniriignated' 95 and these roll upon a bottom race plate 96 seated on the bottom of the counterbore. It will be ap-v preciated that if rotary force is applied 4to the hook', 'it

and its shank84 may turn freely with respect to the scale body on the bearing rollers 95.

As. previously noted, all of the components contained within the cylinder 10 are assembled from thelower end,

- with the exception of the shank 48 of vthe suspension eye.

It will be apparent that after the piston 12 is inserted,

the shank 48 is pushed in from above and then-locked.Y from the underside of the piston by the insertion of" the `lock ring sections 50 and retaining ring'55 and snap' ring 56. The bearing ring 62 is also inserted over and secured to the lower end of the shank from beneath. This ispreferably done after t-he bearing plate 160 isv inserted, since wthis facilitates the insertion ofthe-bearing balls 65. The

bearing plate 60 is preferably locked against downward displacement by a plurality of abut-ments 98 (only'one of which is shown in the drawing) extending upwardly fromy the top of bottom head 75. These may, as shown, Y comprise machine screws fitted inv suitably positioned tapped holes in the head and heldin preliminarilyV adljusted positioning asby a lockA nut 100.

Any important consideration in achieving accuracy` and assembly. The-rollers of the bearing assembly are des- 'Y ameters of said wallportions decreasing progressively though theA pressure uid is, entirely above the piston, in orderfto keep vout atmospheric. moisture and'V minimize oxidation? The apertures 61. allow'the space below bearing support plate., 60 to act asi a part of the air chamber below ttl'ie piston, thereby-reducing the lcompression ratio and, thus, -the range ofrpressure variance and the resistance to piston movement developed below the piston. A limp annular weather seal' member as V105 may also be providedatthe top, bridging, and ysecured lat its inner andouter peripheries to, pilot neck 35 and head ring 26, respectively. y v Y 'While it wil-l1 be apparent thaty the preferred'` embodiment of the invention herein described is well calculated to fulfill the objects and advantages firstV above-stated, it

will be appreciated that the invention isfsusceptiblev to variation, modification and change without` departing `Iclaim:, Y f.

1;. In a hydraulic weighing scale construction, a hollow "c ylinderincluding a plurality of internal cylindrical wall portions of different diameters andhaving. a head closure member atg one end provided with an axially positioned aperture defining-y a, hardened internal surface, said difrom said end of the cylinder toward the other end, a

`piston fitted in said cylinder and having a skirt portion operatively intertted with afwall portion of said cylinder of intermediate diameter, an annular bearing member :fitttedinto saidv cylinder onl the opposite side of said skirt portion fromsaid closure memberv and held` in aportion Aof said cylinder which. is larger than the cylinder portion jwithwhich the lskirt portion is intertted and which is v spaced from said pistonY in an axial direction, saidY annular bearingI member havingA a' hardened and apertured internal bearing portion deiiningt anlaperture-y extending sensitivityin a hydraulic scale is-,the reduction ofV fricn `tion to an absolute minimum. The use of a piston, rather than a diaphragm, is desirable from the standpoint of accuracy and linearity. `In the present construction the largest' portion 69 of the pistonl is so fitted as to move freely but 'accurately withinthe cylinder. It will be appreciated that the actual' travel` is very slight, being ofthe vorder of a f'ew'thousandthsofY auf inch inaxiinuni-V for a ltherethrouglr coaxially with respectf to the piston, a re- 'ducedf bearing supporting portion concentricallyriixed. to -the piston and extending upwardlyfrom said skirt portion into intertted relation with, but ofsubstantially smaller Idiameter than, tlie first-mentioned'v aperture-dening. surrfacer a liarden'edlring on said bearing-supporting portion, i' antifrictionk bearingqmean's-reactin'g against said. ring and vaga'ins'rsaitl hardened surface'of the. headv closuremem-l ber, a second reduced bearing supporting portion concentrically xed to said piston and projecting downwardly from said skirt portion into interfitted relation with, but being of substantially smaller diameter than said aperture in the annular bearing member, a hardened ring on said second bearing-supporting portion, and antifriction bearing means coacting with said last-mentioned ring and with the aperture in the annular bearing member.

2. Means as deiined in claim 1 wherein said head closure member is of graduated external diameter and has its portion of larger diameter facing said skirt portion of the piston and is interlitted with a similarly graduated internal surface of the cylinder, being thereby locked against movement away from the skirt portion.

3. Means as defined in claim 1 wherein said head closure member is of graduated external diameter and has its portion of larger diameter facing said skirt portion of the piston and is interlitted with a similarly graduated internal surface' of the cylinder, being thereby locked against movement away from the skirt portion, said skirt portion being spaced from said head closure member to define a pressure space, an O-ring-type seal carried by said first-mentioned reduced bearing-supporting portion and sealing the same with respect to said head closure member, and a second O-ring-type seal carried by said skirt portion and sealing the same with respect to the cylinder.

4. In a hydraulic scale or the like, a hollow metallic cylinder having a head at one end, a piston reciprocable in the cylinder, a pilot neck extending rigidly from and forming a fluid-tight extension of the piston on one side of the latter and extending slidably through an aperture in said head, bearing and sealing portions for guiding and sealing the pilot neck with respect to the head, tensioning means also connected to the piston for urging the piston toward said head to pressurize a liquid trapped between the piston and head, said tensioning means extending outwardly from the piston in the same direction as said neck and being accessible from outside said head, a transverse bearing support rigid with respect to said cylinder on the opposite side of said piston from said head, a pilot portion extending rigidly from the other side of said piston to travel therewith and slidable in an aperture in said bearing support, coacting bearing portions carried by said pilot portion and bearing support, said neck and pilot portion being of substantially smaller diameter than the piston, and said bearing portions holding the piston against axial misalignment with respect to the cylinder, said bearing portions including opposed hard metallic sections carried by said neck and head, and bearing balls interposed between and reacting against said opposed sections, opposed hard metallic sections carried by said pilot portion and support, bearing balls interposed between and reacting against said last-mentioned sections, and second tensioning means secured to said cylinder and extending in the opposite direction from said first-mentioned tensioning means.

References Cited in the ile of this patent UNITED STATES PATENTS 1,798,076 Frisch Mar. 24, 1931 1,822,628 Lincoln Sept. 8, 1931 2,532,663 Ellis Dec. 5, 1950 2,643,873 Wise June 30, 1953

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